/Engine/Plugins/Runtime/OpenXR/Source/OpenXRHMD/Public/IOpenXRExtensionPlugin.h
Register module as an extension on startup. It is common to do this in StartupModule of yourIModuleInterfaceclass (which may also be the class that implements this interface). The module's LoadingPhase must be PostConfigInit or earlier because OpenXRHMD will look for these after it is loaded in that phase.
void RegisterOpenXRExtensionModularFeature()